I have a bitcoin client installed on machine one. Let's say it has 5 coins in there. I then have another machine, with another client on it. Can both machines see the same wallet?
Do I have to have a per machine wallet? What if I want to pool my coins in one place?
It is a bad idea to have multiple copies of your wallet.dat running from multiple computers if both will be spending. You risk getting double spend attempts that will never confirm and cannot be cleared without performing wallet surgery.
BlockChain.info/wallet has a "desktop sync" feature that will let their hybrid EWallet sync with your Bitcoin.org client (through RPC), but since BlockChain.info/wallet can be used on multiple machines why not just use BlockChain.info/wallet from everywhere instead? You get to use the mobile app with it as well.
You can copy your wallet over multiple machines, but you should generally not do that. Besides, your wallets would start drifting apart with each use - generally Bitcoin keeps a set of spare keys in case you need to use them in the future, and the set is refilled every now and then with random new keys.
The best practices for using Bitcoin is to have backups of wallets, but not use them on multiple machines at the same time. If you want to access your coins from anywhere, you can either look into running Bitcoin in a server mode (a bit tricky, not really for beginners), or using one of the many eWallets available around (you trust your coins to a third party, but this option is quite easy [just don't put too much money there;) ]).
